1. Field of the Invention
The present invention relates to a sewing machine having an automatic thread cutting mechanism, and more particularly to a sewing machine having an automatic thread cutting device which can detect whether or not a thread cutting operation is being carried out in an OFF operation of a power supply when the power supply is turned ON again after the power supply is suddenly turned OFF and can be operated to be returned into a non-thread cutting state if the thread cutting operation is being carried out.
2. Related Art
Japanese Patent No. 2765113 has disclosed a technique in the stoppage of a thread cutting operation in the middle in a thread cutting device of a sewing machine. Referring to the contents of the patent, in the case in which a motor is stopped by a tension of a thread during the thread cutting operation, the motor is started again, thereby completing the thread cutting operation.
However, there is a possibility that a power supply might be suddenly turned OFF for various reasons, that is, a service interruption, power-OFF caused by a careless mistake in a switching operation or forcible power-OFF caused by the generation of an emergency such as a dangerous state during a thermal cutting operation.
In the technique, there is no guarantee that a proper operation is carried out in such a case. The technique according to the patent can be simply applied if the power supply is turned ON and the motor is stopped by an external force.
In the case in which the power supply is turned OFF in the thread cutting operation, therefore, it is necessary to carry out a work for removing a thread from the thread cutting device and reattaching the thread depending on the state of the thread cutting operation immediately after the power supply is turned OFF.